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Full text of "Text Book Of Mechanical Engineering"

664             Zeuner Diagram for Meyer Valve.

(4)  Given travel, or opening to steam or exhaust; also both
laps, and lead.    Strike travel circle and mark points w, Y, and x;
diameter BW being known, the steam circle is struck and BA
found;  and the rest easily completed.

(5)  Given steam opening for any particular position of crank,
position of crank at cut-off, amount o   lead, and exhaust lap.
This is answered at (i) Fig. 654.  .Draw opening i, 2:.lead i:
position of crank for that opening, 3 : and position of crank at
cut-off, 4.    Drop perpendiculars 5 and 6.    Draw 7 at 90° to 4>
and 8 at 90° to 3.    Bisect angle 5, 7, by line .9 ; and angle 8, 6,
by line 10.    Their meeting point is the centre of the- diagram,
the dark line shewing the primary circle.

(6)  Given the lead, and the  positions  of crank at cut-off,
release, and compression.    See Fig. 654, diagram (2).    Let i be
the lead, while 2, 3, 4 are the positions of crank at cut-off, release
and compression respectively.    Drop perpendicular 5 and draw
6 at 90° to 2.    Bisect 5, 6, by 7-, and 4, 3, by 8; their meeting
point being the centre of the diagram,

(7)  Given lead, maximum opening of steam port, and position
of crank at cut-off; also inside lap.    For solution see (3) Fig. 654.
Let i be the lead, i 2 the greatest steam opening, and 3 the
angle of crank at cut-off.    Drop the perpendicular 4, and erect 5.
Draw 6 at right angles to 3, cutting 4 in A.    Bisect 4, 6, by 7,
and produce at 8 to G: join 9,    Draw 10 horizontally, and with
centre A strike n; join AB by 12.     Draw  13 parallel to 12,
cutting 7 in E, which is the centre of the diagram.

Zeuner Diagram for Meyer Valve.—Concerning cut-
off point only, the real opening to steam will be due to the
relation between main and expansion valves at any moment. In
Fig. 655, let AB be the stroke of the main valve, CG its, steam
circle, and 0 the angle of advance. Also let 6^ be the angle of
advance of the expansion eccentric (nearly opposite the engine
crank), and c £ its throw* Taking position ;E, c F would be the
movement of main valve from central position, aud CD that of the
expansion valve, the difference or relative motion being DF,
Measuring this difference at GJ for several positions sux% as E,
CJTK is found, which may be proved to be a circle. To ftnd GK
directly, join HG and 'complete the parallelogram HK, fcy,parallels